Tucked away in the eastern rim of the Sudbury Basin, the Nickel Rim South deposit has hidden its potential for decades. A recent change in its exploration strategy has allowed Falconbridge Ltd. to unearth the importance of Nickel Rim.
“We used to look for elephants, but haven’t had much luck finding them,” Al Hayward, vice-president of mining, told CMJ. “Then we asked ourselves, if elephants are extinct, what else can we look for?”
Pretty soon the geology department came up with the answer: higher-value footwall deposits. This is the shift in thinking that made the Nickel Rim South discovery possible. That plus the most advanced geophysical technology available.
“We dropped a UTEM IV 3-component low frequency Lamontagne geophysics probe down an old hole, MAC-100. Based on the geophysics results we were then able to vector a wedge cut into the detected conductor. Nickel Rim South was Falconbridge’s first discovery made with this improved technology,” said Hayward, then added, “Half of Nickel Rim South is a contact deposit.”
Discovery hole MAC-100 was reported in November 2001. First one 6-m footwall vein was intersected, then another and another until six were cut. The mineralization lies about 1,600 m below the surface. There are significant values between the veins, as well.
Thus far the inferred resource of the footwall zone is estimated at 13.7 million tonnes grading 1.7% Ni, 3.6% Cu, 0.04% Co, 0.8 g/t Au, 2.0 g/t Pt and 2.2 g/t Pd. The deposit is open up-dip.
Mineralization is primarily chalcopyrite, which makes Nickel Rim South more of a copper mine than anything. If it were called a nickel mine, the byproduct copper and PGM netbacks will make the cost of mining and processing a pound of nickel negative US$0.65. Simply put, mining this deposit could cut Falconbridge’s total integrated nickel cash operating costs per pound of nickel by 40% and secure its future in Sudbury for at least another 20 years.
Based on such a buoyant economic outlook, Falconbridge has launched a $590-million underground exploration project.
“The goal is to get down [into the deposit] as quickly as possible and get a measured resource,” Hayward said. There is some urgency to the project because several of Falconbridge’s other mines near Sudbury are nearing the end of their economic lives.
The project calls for two shafts to be sunk simultaneously. Cementation Canada Inc. (formerly Cementation Skanska) won the shaft sinking and station development contract worth more than Cdn$100 million, and will begin work in February 2005. When Cementation finishes its job, Nickel Rim South will have a 7.6-m-diameter, 1,785-m-deep production/service shaft and a 6.1-m-diameter, 1,675-m-deep ventilation/emergency shaft.
Consideration is also being given to building in options for future deepening or an increase in annual capacity, according to Hayward.
Over 10,000 m of lateral development is planned from which to run a >100,000-m drilling program. One exploration level will be developed from the main shaft at the 1,480-m level and ramped down to 1,500 m. Another will be developed from the second shaft at the 1,660-m level.
By the time the underground exploration is completed, three permanent service and production hoists will be installed in the main shaft as well as a permanent cage hoist and a temporary sinking hoist in the second shaft. The ore- and waste-handling infrastructure will be ready and a dewatering system established.
Completing so much development work at the same time the orebody is defined, makes Nickel Rim South a very fast-track project. Site preparation began only in March 2004. The project timetable reserves two years for shaft sinking, with underground lateral development to begin in February 2007. Phase 1 exploration drilling will start in January 2008 and be completed in November of the same year. The mine will be in production at 60% of its planned rate in December 2009. Full production–currently estimated at 1 million tonnes/year–will be reached during 2010. Annual outputs could be as high as 15,000 tonnes of nickel, 45,000 tonnes of copper, 60,000 oz of platinum, 70,000 oz of palladium and 25,000 oz of gold.
The total cost of the exploration and development project will probably top Cdn$800 million, minus pre-production revenue.
Ore from the Nickel Rim South mine will most likely be processed at Falconbridge’s existing Strathcona mill about 30 km to the west. The plant may require some modifications to optimize the recoveries of the various metals. The Nickel Rim South ore is considered to be equally divided among nickel, copper and PGM values.
The project is located about 5 km from the smelter and less than 3 km from the Sudbury airport. The site contains tailings from the old Nickel Rim mine, which was active from 1953 to 1958. Falconbridge treats acidic run-off from the site at the smelter, and this practice will continue.
Using the old tails as backfill in the new mine may be possible, said Hayward. But a final decision on this, or building a new mill at the Nickel Rim South mine, and many other technical details, are further in the future.
“Our goal right now is to get these two exploration levels done,” he said, “and if everything goes as planned, get Nickel Rim South into production.”
That just about sums up mine-making: stir up new ideas, use the most advanced technology and commit ample money. And when a deposit like Nickel Rim South comes along, be prepared to move quickly and reap the rewards.